This invention relates to a magnetic recording medium.
Heretofore, magnetic tapes and discs have been widely used as recording media. They generally have consisted of polyester films, stretched PVC films, etc, coated with a magnetic material in which finely divided particles of a ferromagnetic substance such as gamma-Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, etc are dispersed. Recording has been by magnetization within the plane of the surface of the film, for example.
From the viewpoint of magnetic characteristics, the above types of materials may be termed semi-hard magnetic materials, and can be readily magnetized. Since the material does not self-demagnetize, in an external magnetic field of about 100 oe (oersted), as would a soft magnetic material, the material has the advantages of high density recording, and easy repeated recording and erasure. However, this type of magnetic recording material also has numerous disadvantages. For example, when the magnetic recording tape is transported with the magnetically coated surface in contact with the magnetic head having an air gap, abrasion of the magnetic head and of the magnetically coated surface is inevitable, thereby resulting in deterioration of the recording characteristics. Furthermore, recorded information can be readily changed, either deliberately or accidently, by use of an external magnetic field.